Spindle motors are widely used in electronic appliances (e.g., a projection television, a hometheater device, a drive for a computer, etc.) requiring precisely rotational devices. The spindle motors are small in size and can rotate at high speed. Also, the spindle motors are easy to precisely control and have low power consumption. Because of these advantages, the use of the spindle motors is expected to increase.
Hereunder, a related art spindle motor will be described.
FIG. 1 is a sectional view of a related art slim-type spindle motor.
Referring to FIG. 1, the related art slim-type spindle motor 10 includes a base plate 11, a printed circuit board (PCB) 12, a bearing housing 13, a bearing 14, a core 18, a washer 15, a thrust plate 16, and a thrust stopper 17. Also, a rotor is inserted into the bearing 14 to perform a rotational movement.
An assembly process of the slim-type spindle motor 10 will be described below. First, the bearing 14 is press-fit into the bearing housing 13. The washer 15, the thrust plate 16, and the thrust stopper 17 are assembled in a lower side of the bearing housing 13. Thereafter, the bearing housing 13 is coupled to the base plate 11. At this time, the thrust stopper 17 and the base plate 11 are coupled to end portions a and b of the bearing housing 13 by caulking.
Also, the core 18 is coupled to the bearing housing 13 in a state that the PCB 12 is fixed to the base plate 11. The core 18 is supplied with power from the PCB 12.
After the stator is assembled through the above-described processes, the rotor (not shown) is inserted into the bearing housing 13. The rotor includes a shaft, a rotor yoke, and a permanent magnet. The rotor is rotated by a repulsive magnetic force between the core 18 and the rotor.
Preferably, the bearing housing 13 and the base plate 11 are exactly perpendicular to each other. However, since the bearing housing 13 is inclined at an angle ranging from the minimum 2˜3′ to the maximum 10′ with respect to an imaginary vertical line, a disk rotated by the spindle motor 10 collides against an inside of a drive.
To solve the above problems, a process for correcting a shaft perpendicularity is carried out. That is, after the bearing housing 13 is finally assembled, it is forcibly pressed in a state that the bearing housing 13 is inserted into an assembly jig. In this process, a physical press is applied to the bearing housing 13 on the basis of three points of the base plate 11. This process is called a “shaft perpendicularity adjusting process”.
However, when an excessive force is applied during the shaft perpendicular adjusting process, the bearing housing 13 and the bearing 14 may be deformed and the shaft may be again inclined by a spring-back shape of the assembly structure even after the shaft perpendicularity is corrected.
Also, among the entire processes of manufacturing the spindle motor 10, the shaft perpendicularity adjusting process is complicate and its accuracy is difficult to obtain. That is, the shaft perpendicularity adjusting process often causes defective spindle motors and decreases the productivity of the spindle motors.
A structure of another related art spindle motor, namely half height spindle motor, will now be described.
FIG. 2 is a sectional view of a related art half height spindle motor.
Referring to FIG. 2, the half height spindle motor 20 includes a bearing housing 21, a base plate 22, a PCB 23, a thrust plate 24, a bearing 25, and a core 26.
Specifically, the bearing housing 21 has a thrust stopper integrally formed on a lower surface, without separate thrust stopper as shown in FIG. 1, and is press-fit into the base plate 22 including a burred portion c.
Also, the thrust plate 24 and the bearing 25 are inserted through an upper portion of the bearing housing 21. The core 26 is not supported by the PCB 23, but is adhered to the bearing housing 21 by an adhesive, or press-fit into the bearing housing 21.
However, when the core 26 is adhered to or press-fit into the bearing housing 21 without any additional supporting structure, the adhesive takes a lot of time to harden. When a gap is formed between the core 26 and the housing 21, the press-fit is impossible, or they are coupled at an incorrect position. Moreover, when the inner diameter of the core 26 is too small or the outer diameter of the housing 21 is too large, a large amount of press-fit is applied, causing the deformation of the core 26.
Meanwhile, the bearing supporting structure such as the half height spindle motor of FIG. 2 may be applied to the slim-type spindle motor 10 of FIG. 1. However, since the base plate 11 used in the slim-type spindle motor is relatively thin (about 0.6-0.8 mm), the base plate 11 may be deformed by the press-fit. Thus, this case is difficult to actually apply. In order to form the burred portion c on the base plate 11 of the slim-type spindle motor 10, the base plate 11 must be thicker. Accordingly, it is difficult to fabricate the spindle motor with slim profile.
Due to these problems, it is difficult to apply the bearing supporting structure of the half height spindle motor to the slim-type motor.